1. Field of the Invention
The invention relates to photocopy machines, and particularly to the type in which the original document is supported in a reciprocating carrier for moving the document through the exposure station. More particularly, the invention relates to a photoelectric paper cut-off sensor which detects automatically the size of the original and actuates a knife which cuts each copy to the exact size of the original, without being programmed manually by an operator.
2. Description of the Prior Art
Recent years have seen considerable advancement in xerography or document reproduction apparatus, commonly referred to as photocopy machines. These photocopy machines generally are of two main catagories depending upon the handling of the original document by the machine. In one type of photocopy machine the original is moved through the machine on a belt conveyor or roll mechanism in conjunction with a sheet or continuous web of copy paper through the exposure station. Such feedthrough machines possess the inherent danger of the original becoming stuck, lost or mutilated within the machine, requiring partial machine disassembly to retrieve the same, as well as possible damage to the only available copy or valuable document.
Another type of photocopy machine uses a carrier for supporting the original document which in turn is reciprocated across the top of a housing during the exposure period. Many of these carrier-type photocopy machines use individual sheets of electrostatic copy paper stored in stack form within the machine, such as shown in U.S. Pat. Nos. 3,424,526, 3,604,796 and 3,672,762. Other carrier-type photocopy machines use a roll of continuous copy paper which moves through the machine in conjunction with the moving document carrier. A cut-off knife is mounted within these machines for severing of the continuous web of copy paper, depending upon the size of the original document.
The cut-off knife usually is controlled by a mechanically programmed or adjusted limit switch or the like which is set by the operator upon placing of the original in the carrier so that the copy paper is cut to the approximate length of the original to prevent waste. Examples of such machines are shown in U.S. Pat. Nos. 3,740,132 and 3,751,158.
Such manual setting usually positions a trip lever or the like which in turn contacts an electrical limit switch upon passage of the original to energize and actuate the cut-off knife. Problems occur in the operation of such machines, especially when the machines are used by inexperienced and a number of operators as in a large office. In such situations, the operator may not understand the mechanical setting procedure, and many times merely neglects to set the mechanical cut-off control. This results in excess copy paper, or faulty copies due to too short of copy paper.
Thus, the need has existed for a control mechanism which is of a relatively simple and inexpensive design for a photocopy machine which senses automatically the size of the original document and actuates the cut-off knife for the copy paper. No known mechanism or equipment of which we are aware uses a photoelectric sensor for this purpose in the particular manner set forth below for achieving these results.
Various photocopy machines use photoelectric sensors in the operation of the machine, but in a different manner than described below and set forth in the attached claims.
A photocopy machine described in U.S. Pat. Nos. 3,473,035 uses a plurality of photosensors in conjunction with openings in a document transport belt for sensing the size of the original to register the document correctly in the exposure zone, and not for actuation of a copy paper cut-off knife.
U.S. Pat. No. 3,536,401 discloses another photosensor mechanism in a photocopy machine in which the original is transported through the machine on a conveyor belt-type system in which the length of the original is sensed for actuation of the copy paper cut-off knife. The photosensor must be manually adjusted for the various lengths of originals so that the copy paper length corresponds to the length of the original and does not cut off the copy paper automatically to original documents of various lengths.
U.S. Pat. No. 3,689,143 discloses another photocopy machine which uses a plurality of photoelectric sensors which sense the width of the original document for selecting the proper size copy sheet for transporting to the exposure station from a plurality of stacks of copy sheets.
U.S. Pat. No. 3,879,125 discloses still another type of photocopy machine using a plurality of photoelectric sensors for controlling the speed of travel of the original document and the copy paper based upon the position of the leading edge of the original which is sensed by the photosensors.